body{
    margin: 0px;
}
*{
    box-sizing: border-box;
}
/*display*/
.display_flex{
    display: -webkit-box; /* Chrome 4+, Safari 3.1, iOS Safari 3.2+ */
    display: -moz-box; /* Firefox 17- */
    display: -webkit-flex; /* Chrome 21+, Safari 6.1+, iOS Safari 7+, Opera 15/16 */
    display: -moz-flex; /* Firefox 18+ */
    display: -ms-flexbox; /* IE 10 */
    display: flex;
}
.align-items_center{
    -webkit-box-align: center;
    -ms-flex-align: center;
    -webkit-align-items: center;
    align-items: center;
}
.justify-content_flex-justify-center{
    -webkit-box-pack: justify;
    -ms-flex-pack: justify;
    -webkit-justify-content: center;
    justify-content: center;
}